scholarly journals Activation of Neurokinin 3 Receptors in the Median Preoptic Nucleus Decreases Core Temperature in the Rat

Endocrinology ◽  
2011 ◽  
Vol 152 (12) ◽  
pp. 4894-4905 ◽  
Author(s):  
Penny A. Dacks ◽  
Sally J. Krajewski ◽  
Naomi E. Rance
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Core Temperature ◽  
Ovariectomized Rats ◽  
Dependent Manner ◽  
Preoptic Nucleus ◽  
Ambient Temperatures ◽  
Median Preoptic Nucleus ◽  
Estrogen Withdrawal ◽  
Neurokinin 3 Receptor

Estrogens have pronounced effects on thermoregulation, as illustrated by the occurrence of hot flushes secondary to estrogen withdrawal in menopausal women. Because neurokinin B (NKB) gene expression is markedly increased in the infundibular (arcuate) nucleus of postmenopausal women, and is modulated by estrogen withdrawal and replacement in multiple species, we have hypothesized that NKB neurons could play a role in the generation of flushes. There is no information, however, on whether the primary NKB receptor [neurokinin 3 receptor (NK3R)] modulates body temperature in any species. Here, we determine the effects of microinfusion of a selective NK3R agonist (senktide) into the rat median preoptic nucleus (MnPO), an important site in the heat-defense pathway. Senktide microinfusion into the rat MnPO decreased core temperature in a dose-dependent manner. The hypothermia induced by senktide was similar in ovariectomized rats with and without 17β-estradiol replacement. The hypothermic effect of senktide was prolonged in rats exposed to an ambient temperature of 29.0 C, compared with 21.5 C. Senktide microinfusion also altered tail skin vasomotion in rats exposed to an ambient temperature of 29.0 but not 21.5 C. Comparisons of the effects of senktide at different ambient temperatures indicated that the hypothermia was not secondary to thermoregulatory failure or a reduction in cold-induced thermogenesis. Other than a very mild increase in drinking, senktide microinfusion did not affect behavior. Terminal fluorescent dextran microinfusion showed targeting of the MnPO and adjacent septum, and immunohistochemical studies revealed that senktide induced a marked increase in Fos-activation in the MnPO. Because MnPO neurons expressed NK3R-immunoreactivity, the induction of MnPO Fos by senktide is likely a direct effect. By demonstrating that NK3R activation in the MnPO modulates body temperature, these studies support the hypothesis that hypothalamic NKB neurons could be involved in the generation of menopausal flushes.

scholarly journals Neurokinin 3 Receptor-Expressing Neurons in the Median Preoptic Nucleus Modulate Heat-Dissipation Effectors in the Female Rat

Endocrinology ◽  
2015 ◽  
Vol 156 (7) ◽  
pp. 2552-2562 ◽  
Author(s):  
Melinda A. Mittelman-Smith ◽  
Sally J. Krajewski-Hall ◽  
Nathaniel T. McMullen ◽  
Naomi E. Rance
Keyword(s):  
Heat Dissipation ◽  
Medial Septum ◽  
Ovariectomized Rats ◽  
Female Rat ◽  
Preoptic Nucleus ◽  
Ambient Temperatures ◽  
Median Preoptic Nucleus ◽  
Cutaneous Vasodilation ◽  
Neurokinin 3 Receptor ◽  
Kndy Neurons

KNDy neurons facilitate tail skin vasodilation and modulate the effects of estradiol on thermoregulation. We hypothesize that KNDy neurons influence cutaneous vasodilation via projections to neurons in the median preoptic nucleus (MnPO) that express the neurokinin 3 receptor (NK3R). In support of this hypothesis, focal microinjections of senktide, an NK3R agonist, into the MnPO lowers core temperature (TCORE) in the female rat. To further study the role of MnPO NK3R neurons in thermoregulation, these neurons were specifically ablated using a conjugate of a selective NK3R agonist and saporin (NK3-SAP). NK3-SAP or blank-SAP (control) was injected into the MnPO/medial septum. Tail skin temperature (TSKIN) and TCORE were measured in ovariectomized rats exposed to 3 ambient temperatures (TAMBIENT) before and after estradiol-17β (E2) treatment. Before killing, we injected senktide (sc), monitored TCORE for 70 minutes, and harvested brains for Fos immunohistochemistry. Ablation of MnPO NK3R neurons lowered TSKIN at neutral and subneutral TAMBIENT regardless of E2 treatment. However, ablation did not prevent the effects of E2 on TCORE and TSKIN. In control rats, senktide injections induced hypothermia with numerous Fos-immunoreactive cells in the MnPO. In contrast, in NK3-SAP rats, senktide did not alter TCORE and minimal Fos-immunoreactive neurons were identified in the MnPO. These data show that NK3R neurons in the MnPO are required for the hypothermic effects of senktide but not for the E2 modulation of thermoregulation. The lower TSKIN in NK3-SAP–injected rats suggests that MnPO NK3R neurons, like KNDy neurons, facilitate cutaneous vasodilation, an important heat-dissipation effector.

Sleep-related c-Fos protein expression in the preoptic hypothalamus: effects of ambient warming

2000 ◽  
Vol 279 (6) ◽  
pp. R2079-R2088 ◽  
Author(s):  
Hui Gong ◽  
Ronald Szymusiak ◽  
Janice King ◽  
Teresa Steininger ◽  
Dennis McGinty
Keyword(s):  
Protein Expression ◽  
Ambient Temperature ◽  
Neuronal Activity ◽  
Preoptic Area ◽  
Thermal Stimulation ◽  
Preoptic Nucleus ◽  
Ambient Temperatures ◽  
Median Preoptic Nucleus ◽  
Fos Protein ◽  
Stimulation Of

Preoptic area (POA) neuronal activity promotes sleep, but the localization of critical sleep-active neurons is not completely known. Thermal stimulation of the POA also facilitates sleep. This study used the c-Fos protein immunostaining method to localize POA sleep-active neurons at control (22°C) and mildly elevated (31.5°C) ambient temperatures. At 22°C, after sleep, but not after waking, we found increased numbers of c-Fos immunoreactive neurons (IRNs) in both rostral and caudal parts of the median preoptic nucleus (MnPN) and in the ventrolateral preoptic area (VLPO). In animals sleeping at 31.5°C, significantly more Fos IRNs were found in the rostral MnPN compared with animals sleeping at 22°C. In VLPO, Fos IRN counts were no longer increased over waking levels after sleep at the elevated ambient temperature. Sleep-associated Fos IRNs were also found diffusely in the POA, but counts were lower than those made after waking. This study supports a hypothesis that the MnPN, as well as the VLPO, is part of the POA sleep-facilitating system and that the rostral MnPN may facilitate sleep, particularly at elevated ambient temperatures.

Sleep-waking pattern and body temperature in hypoxia at selected ambient temperatures

1984 ◽  
Vol 57 (5) ◽  
pp. 1564-1568 ◽  
Author(s):  
B. Hale ◽  
D. Megirian ◽  
M. J. Pollard
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Core Temperature ◽  
Ambient Temperatures ◽  
State Changes ◽  
Maximum Minimum ◽  
Mild Hypoxia ◽  
Low Ambient Temperature

We studied the effect of mild hypoxia (15% O2) and low ambient temperature (Ta = 15 degrees C) on the rat's sleep-waking pattern (SWP) and maximum-minimum core temperature (max-min Tb). Mild hypoxia at neutral Ta (29 degrees C) disrupted the SWP in the same way as low Ta during normoxia: both affected the pattern of frequency of state changes (P less than 0.01), not the pattern of epoch durations. Mild hypoxia and low Ta together caused a degree of disruption of the SWP which was the sum of each alone, i.e., additive. Although both mild hypoxia and low Ta significantly depressed max-min Tb, low Ta exerted a greater effect than mild hypoxia. Together they further depressed max-min Tb in an additive way. We conclude that mild hypoxia disrupts the rat's SWP independent of central thermoregulatory mechanisms at neutral Ta, that the effects of mild hypoxia and low Ta on the SWP are additive at the stimulus levels used, and that Ta, not inspired O2, determines Tb.

scholarly journals Effects of Estradiol on the Thermoneutral Zone and Core Temperature in Ovariectomized Rats

Endocrinology ◽  
2010 ◽  
Vol 151 (3) ◽  
pp. 1187-1193 ◽  
Author(s):  
Penny A. Dacks ◽  
Naomi E. Rance
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Ovariectomized Rats ◽  
Neural Pathways ◽  
Estradiol Treatment ◽  
Ambient Temperatures ◽  
Thermoneutral Zone ◽  
Estrogen Withdrawal ◽  
Estradiol 17Β ◽  
Loss Mechanisms

Hot flushes represent a disorder of central thermoregulation characterized by the episodic activation of heat loss mechanisms. Although flushes are associated with estrogen withdrawal, there is little understanding of the effects of estrogen on thermoregulation in any species. It has been proposed that hormone withdrawal increases the sensitivity of hypothalamic neural pathways that control heat dissipation effectors. If so, we predicted that ovariectomized rats without estradiol treatment would activate tail skin vasodilatation (a major heat loss effector) at lower ambient temperatures and thereby lower the thermoneutral zone. The thermoneutral zone, defined as the range of ambient temperatures in which thermoregulation is achieved only by sensible (dry) heat loss, was evaluated based on properties of skin vasomotion. Core and tail skin temperatures were recorded in ovariectomized rats (with and without estradiol-17β) exposed to ambient temperatures from 13 to 34 C in an environmental chamber. Rats without estradiol exhibited increased skin vasodilatation and a shift in the thermoneutral zone to lower ambient temperatures. Moreover, the ambient temperature threshold for skin vasodilatation was significantly lower in rats without estradiol treatment. At most ambient temperatures, average core temperature was unaffected by estradiol. However, at ambient temperatures of 32.5 C and above, untreated ovariectomized rats exhibited higher core temperatures compared with estradiol-treated rats. Thus, estradiol-17β treatment enhanced the maintenance of core temperature during heat exposure. These findings support the hypothesis that estrogen withdrawal increases the sensitivity of thermoregulatory neural pathways and modifies the activation of heat loss mechanisms.

Ambient temperature effects on physiological traits of white-tailed deer

1975 ◽  
Vol 53 (6) ◽  
pp. 679-685 ◽  
Author(s):  
J. B. Holter ◽  
W. E. Urban Jr. ◽  
H. H. Hayes ◽  
H. Silver ◽  
H. R. Skutt
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Energy Expenditure ◽  
Ambient Temperature ◽  
Temperature Effects ◽  
Temperature Changes ◽  
Wind Chill ◽  
Ambient Temperatures ◽  
Energy Equilibrium ◽  
Body Energy

Six adult white-tailed deer (Odocoileus virginianus borealis) were exposed to 165 periods of 12 consecutive hours of controlled constant ambient temperature in an indirect respiration calorimeter. Temperatures among periods varied from 38 to 0 (summer) or to −20C (fall, winter, spring). Traits measured were energy expenditure (metabolic rate), proportion of time spent standing, heart rate, and body temperature, the latter two using telemetry. The deer used body posture extensively as a means of maintaining body energy equilibrium. Energy expenditure was increased at low ambient temperature to combat cold and to maintain relatively constant body temperature. Changes in heart rate paralleled changes in energy expenditure. In a limited number of comparisons, slight wind chill was combatted through behavioral means with no effect on energy expenditure. The reaction of deer to varying ambient temperatures was not the same in all seasons of the year.

scholarly journals Body Temperatures in Some Australian Mammals II.Peramelidae

1962 ◽  
Vol 15 (2) ◽  
pp. 386 ◽  
Author(s):  
PR Morrison
Keyword(s):  
Body Temperature ◽  
Ambient Temperature ◽  
Active Phase ◽  
Temperature Measurements ◽  
Temperature Cycle ◽  
Body Temperatures ◽  
Ambient Temperatures ◽  
Diurnal Temperature

Body temperature measurements on the short-nosed bandicoot (Thylacis obeaulus) have shown a nocturnal cycle with a range of 1� 2�C and a short active phase at 2200-0400 hr. The bilby or rabbit bandicoot (Macrotis lagoti8) had a sharply defined temperature cycle, with a range of almost 3�C after several months of captivity, during which the day-time resting temperature was progressively lowered from 36� 4 to 34� 2�C. Forced activity raised the diurnal temperature substantially but not to the nocturnal level. Forced activity did not raise the nocturnal level which was similar in the two species (37' O�C). Both species could regulate effectively at an ambient temperature of 5�C, but only Thylaci8 showed regulation at ambient temperatures of between 30 and 40�C.

scholarly journals Natural haplotypes of FLM non-coding sequences fine-tune flowering time in ambient spring temperatures in Arabidopsis

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ulrich Lutz ◽  
Thomas Nussbaumer ◽  
Manuel Spannagl ◽  
Julia Diener ◽  
Klaus FX Mayer ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Flowering Time ◽  
Dependent Manner ◽  
Negative Effects ◽  
Vegetative Period ◽  
Temperature Changes ◽  
Ambient Temperatures ◽  
Intron 1 ◽  
Alternatively Spliced ◽  
Spring Temperatures

Cool ambient temperatures are major cues determining flowering time in spring. The mechanisms promoting or delaying flowering in response to ambient temperature changes are only beginning to be understood. In Arabidopsis thaliana, FLOWERING LOCUS M (FLM) regulates flowering in the ambient temperature range and FLM is transcribed and alternatively spliced in a temperature-dependent manner. We identify polymorphic promoter and intronic sequences required for FLM expression and splicing. In transgenic experiments covering 69% of the available sequence variation in two distinct sites, we show that variation in the abundance of the FLM-ß splice form strictly correlate (R2 = 0.94) with flowering time over an extended vegetative period. The FLM polymorphisms lead to changes in FLM expression (PRO2+) but may also affect FLM intron 1 splicing (INT6+). This information could serve to buffer the anticipated negative effects on agricultural systems and flowering that may occur during climate change.

Temperature regulation and cold acclimation in the golden hamster

1965 ◽  
Vol 20 (3) ◽  
pp. 405-410 ◽  
Author(s):  
Hermann Pohl
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Acclimation ◽  
Heat Production ◽  
Golden Hamster ◽  
Thermal Conductance ◽  
Muscular Activity ◽  
The Body ◽  
Ambient Temperatures

Characteristics of cold acclimation in the golden hamster, Mesocricetus auratus, were 1) higher metabolic rate at -30 C, 2) less shivering when related to ambient temperature or oxygen consumption, and 3) higher differences in body temperature between cardiac area and thoracic subcutaneous tissues at all ambient temperatures tested, indicating changes in tissue insulation. Cold-acclimated hamsters also showed a rise in temperature of the cardiac area when ambient temperature was below 15 C. Changes in heat distribution in cold-acclimated hamsters suggest higher blood flow and heat production in the thoracic part of the body in the cold. The thermal conductance through the thoracic and lumbar muscle areas, however, did not change notably with lowering ambient temperature. Marked differences in thermoregulatory response to cold after cold acclimation were found between two species, the golden hamster and the thirteen-lined ground squirrel, showing greater ability to regulate body temperature in the cold in hamsters. hibernator; oxygen consumption— heat production; body temperature — heat conductance; muscular activity — shivering; thermoregulation Submitted on July 6, 1964

scholarly journals Collective thermoregulation in bee clusters

2014 ◽  
Vol 11 (91) ◽  
pp. 20131033 ◽  
Author(s):  
Samuel A. Ocko ◽  
L. Mahadevan
Keyword(s):  
Ambient Temperature ◽  
Core Temperature ◽  
Continuum Model ◽  
External Temperature ◽  
Ambient Temperatures ◽  
Advection Diffusion ◽  
Central Controller ◽  
Buoyancy Driven Flows ◽  
Dense Cluster

Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection–diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective ‘behavioural pressure’, which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioural pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy-driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities and suggests strategies for biomimetic thermoregulation.

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